How do you become the #1 fitness trainer on YouTube? Mix equal parts sex appeal, production values and brutal at-home workouts - and you get married couple Zuzana and Frederick Light.
Their 12-minute routines regularly rack up millions of views. Their top workout has reached almost 9 million plays.
We asked Zuzana and Frederick about the rigors of staying in killer shape and managing a monster YouTube fan base.
CBS News: What's your background? How did you become a fitness guru and junkie?
Zuzana: I am from the Czech Republic and I grew up in very humble surroundings in Prague.
About two-and-a-half years ago I needed some serious butt tightening, so I started to learn about fitness, exercising and diet. My husband and I started BodyRock.tv as a way to vlog about the journey toward getting fit.
CBS News: What is your toughest workout? How do you pack so much calorie burning into just 12 minutes?
Zuzana: Intensity is the key to short workouts, so all of my workouts have to be tough. Ultimately, the intensity depends on how hard you push yourself during the workout.
Burning calories during the workout is not the only benefit of pushing at your maximum effort. This type of training will boost your metabolism and build lean muscles so that your body will be burning calories long after the workout is over.
CBS News: To get in your shape, are you really doing just the workouts we see on your site or you sneaking in three hours in the gym each day?
Zuzana: I don't enjoy going to the gym and believe me, I am always just really happy to have my short brutal workout finished for the day. I am not one of those people who enjoys working out for hours, nor do I believe that it is necessary. I have much better and more fun things to do during the day.
CBS News: Talk about what you eat.
Zuzana: My diet is very simple. I try to avoid processed foods as much as possible, which means that I eat mostly fresh fruits and vegetables. I recently turned vegetarian and I have never felt so light and full of energy.
I like to share a lot of the recipes that I cook at home for my husband on my blog. I like to keep everything simple so even my meals are easy to prepare and are made from just a few basic ingredients.
I believe that food is not simply a fuel. Food is something that should be celebrated and enjoyed as one of the great pleasures of life. Simple always means tasty and healthy in my kitchen.
CBS News: What are your secret vices?
Zuzana: It is not a secret that I have a greedy passion for ice cream. On our recent trip to Italy that my husband and I shared in our travel videos, you can see me gobbling down ice cream in almost every video.
My husband, Frederick, teased me that I tasted every ice cream flavor in the country. It is not something that I would eat on a daily or even weekly basis, but those Italians really know their ice cream and I was on my vacation - that's my excuse.
CBS News: You have a huge following on YoutTube. What do people ask you most often? What are the most inspiring questions you get - and the grossest?
Zuzana: We don't pay any attention to negative comments. We take the same approach to user comments as we do to our thoughts - we try to keep everything very positive.
People are asking all kinds of questions about exercise and diet, but what we find the most inspiring is when people share their personal success stories. When someone shares how they have managed to lose weight and transform their bodies thanks to following our workouts and the tremendous positive impact this makes in their lives,it gives us more motivation to keep going.
CBS News: Your imagery on YoutTube is very sexy. Do you think sex appeal is helping to drive your success?
Zuzana: Of course it has an impact. I think that strength and sex appeal really go hand in hand.
CBS News: What's the biggest motivator you can use to help people to get in shape: sex appeal, health or something else?
Zuzana: Everyone has their own reasons for getting in shape. It is not a bad thing if your biggest motivation is to look sexy and beautiful. The by-products of that will be health, vitality and well-being. Whatever fuels your desire to work out will result in a positive outcome for your life.
CBS News: Do you ever feel like just spending a week in baggy sweats eating ice cream on the couch?
Zuzana: That sounds kind of depressing to me. I don't like sitting on my butt. There are too many things that I would like to accomplish and life is short.
CBS News: Many people on your site ask what about your partner Frederick. Do you whip him into shape or let him slide?
Zuzana: Our blog is about my husband and me and our life together. It really helps to live with someone who has the same goals and shares the same beliefs.
While I have weaknesses in terms of my diet, Freddy is more apt to skip workouts. We both are constantly working on our weak areas, and having each other for support really helps.
CBS News: Tell us something people don't know about you that we weren't smart enough to ask. Zuzana: I used to work at McDonalds, and I used to make love to Big Macs and french fries on almost a daily basis. I am not kidding.